Urea catalytic oxidation for energy and environmental applications.

Urea is one of the most essential reactive nitrogen species in the nitrogen cycle and plays an indispensable role in the water-energy-food nexus. However, untreated urea or urine wastewater causes severe environmental pollution and threatens human health. Electrocatalytic and photo(electro)catalytic urea oxidation technologies under mild conditions have become promising methods for energy recovery and environmental remediation. An in-depth understanding of the reaction mechanisms of the urea oxidation reaction (UOR) is important to design efficient electrocatalysts/photo(electro)catalysts for these technologies. This review provides a critical appraisal of the recent advances in the UOR by means of both electrocatalysis and photo(electro)catalysis, aiming to comprehensively assess this emerging field from fundamentals and materials, to practical applications. The emphasis of this review is on the design and development strategies for electrocatalysts/photo(electro)catalysts based on reaction pathways. Meanwhile, the UOR in natural urine is discussed, focusing on the influence of impurity ions. A particular emphasis is placed on the application of the UOR in energy and environmental fields, such as hydrogen production by urea electrolysis, urea fuel cells, and urea/urine wastewater remediation. Finally, future directions, prospects, and remaining challenges are discussed for this emerging research field. This critical review significantly increases the understanding of current progress in urea conversion and the development of a sustainable nitrogen economy.

Advanced cathodes for aqueous Zn batteries beyond Zn2+ intercalation.

Aqueous zinc (Zn) batteries have attracted global attention for energy storage. Despite significant progress in advancing Zn anode materials, there has been little progress in cathodes. The predominant cathodes working with Zn2+/H+ intercalation, however, exhibit drawbacks, including a high Zn2+ diffusion energy barrier, pH fluctuation(s) and limited reproducibility. Beyond Zn2+ intercalation, alternative working principles have been reported that broaden cathode options, including conversion, hybrid, anion insertion and deposition/dissolution. In this review, we report a critical assessment of non-intercalation-type cathode materials in aqueous Zn batteries, and identify strengths and weaknesses of these cathodes in small-scale batteries, together with current strategies to boost material performance. We assess the technical gap(s) in transitioning these cathodes from laboratory-scale research to industrial-scale battery applications. We conclude that S, I2 and Br2 electrodes exhibit practically promising commercial prospects, and future research is directed to optimizing cathodes. Findings will be useful for researchers and manufacturers in advancing cathodes for aqueous Zn batteries beyond Zn2+ intercalation.

Local reaction environment in electrocatalysis.

Beyond conventional electrocatalyst engineering, recent studies have unveiled the effectiveness of manipulating the local reaction environment in enhancing the performance of electrocatalytic reactions. The general principles and strategies of local environmental engineering for different electrocatalytic processes have been extensively investigated. This review provides a critical appraisal of the recent advancements in local reaction environment engineering, aiming to comprehensively assess this emerging field. It presents the interactions among surface structure, ions distribution and local electric field in relation to the local reaction environment. Useful protocols such as the interfacial reactant concentration, mass transport rate, adsorption/desorption behaviors, and binding energy are in-depth discussed toward modifying the local reaction environment. Meanwhile, electrode physical structures and reaction cell configurations are viable optimization methods in engineering local reaction environments. In combination with operando investigation techniques, we conclude that rational modifications of the local reaction environment can significantly enhance various electrocatalytic processes by optimizing the thermodynamic and kinetic properties of the reaction interface. We also outline future research directions to attain a comprehensive understanding and effective modulation of the local reaction environment.

Nature-Inspired Photocatalytic Azo Bond Cleavage with Red Light.

The emerging field of photoredox catalysis in mammalian cells enables spatiotemporal regulation of a wealth of biological processes. However, the selective cleavage of stable covalent bonds driven by low-energy visible light remains a great challenge. Herein, we report that red light excitation of a commercially available dye, abbreviated NMB+, leads to catalytic cleavage of stable azo bonds in both aqueous solutions and hypoxic cells and hence a means to photodeliver drugs or functional molecules. Detailed mechanistic studies reveal that azo bond cleavage is triggered by a previously unknown consecutive two-photon process. The first photon generates a triplet excited state, 3NMB+*, that is reductively quenched by an electron donor to generate a protonated NMBH•+. The NMBH•+ undergoes a disproportionation reaction that yields the initial NMB+ and two-electron-reduced NMBH (i.e., leuco-NMB, abbreviated as LNMB). Interestingly, LNMB forms a charge transfer complex with all four azo substrates that possess an intense absorption band in the red region. A second red photon induces electron transfer from LNMB to the azo substrate, resulting in azo bond cleavage. The charge transfer complex mediated two-photon catalytic mechanism reported herein is reminiscent of the flavin-dependent natural photoenzyme that catalyzes bond cleavage reactions with high-energy photons. The red-light-driven photocatalytic strategy offers a new approach to bioorthogonal azo bond cleavage for photodelivery of drugs or functional molecules.

Establishing Exceptional Durability in Ultralow-Temperature Organic-Sodium Batteries via Stabilized Multiphase Conversions.

Operation of rechargeable batteries at ultralow temperature is a significant practical problem because of poor kinetics of the electrode. Here, we report for the first time stabilized multiphase conversions for fast kinetics and long-term durability in ultralow-temperature, organic-sodium batteries. We establish that disodium rhodizonate organic electrode in conjunction with single-layer graphene oxide obviates consumption of organic radical intermediates, and demonstrate as a result that the newly designed organic electrode exhibits excellent electrochemical performance of a highly significant capacity of 130 mAh g-1 at -50 °C. We evidence that the full-cell configuration coupled with Prussian blue analogues exhibits exceptional cycling stability of >7000 cycles at -40 °C while maintaining a discharge capacity of 101 mAh g-1 at a high current density 300 mA g-1. We show this is among the best reported ultralow-temperature performance for nonaqueous batteries, and importantly, the pouch cell exhibits a continuous power supply despite conditions of -50 °C. This work sheds light on the distinct energy storage characteristics of organic electrode and opens up new avenues for the development of reliable and sustainable ultralow-temperature batteries.

Aqueous Zinc-Iodine Pouch Cells with Long Cycling Life and Low Self-Discharge.

Aqueous zinc batteries are practically promising for large-scale energy storage because of cost-effectiveness and safety. However, application is limited because of an absence of economical electrolytes to stabilize both the cathode and anode. Here, we report a facile method for advanced zinc-iodine batteries via addition of a trace imidazolium-based additive to a cost-effective zinc sulfate electrolyte, which bonds with polyiodides to boost anti-self-discharge performance and cycling stability. Additive aggregation at the cathode improves the rate capacity by boosting the I2 conversion kinetics. Also, the introduced additive enhances the reversibility of the zinc anode by adjusting Zn2+ deposition. The zinc-iodine pouch cell, therefore, exhibits industrial-level performance evidenced by a ∼99.98% Coulombic efficiency under ca. 0.4C, a significantly low self-discharge rate with 11.7% capacity loss per month, a long lifespan with 88.3% of initial capacity after 5000 cycles at a 68.3% zinc depth-of-discharge, and fast-charging of ca. 6.7C at a high active-mass loading >15 mg cm-2. Highly significant is that this self-discharge surpasses commercial nickel-metal hydride batteries and is comparable with commercial lead-acid batteries, together with the fact that the lifespan is over 10 times greater than reported works, and the fast-charging performance is better than commercial lithium-ion batteries.

Deep Learning Assessment of Small Renal Masses at Contrast-enhanced Multiphase CT.

Background Accurate characterization of suspicious small renal masses is crucial for optimized management. Deep learning (DL) algorithms may assist with this effort. Purpose To develop and validate a DL algorithm for identifying benign small renal masses at contrast-enhanced multiphase CT. Materials and Methods Surgically resected renal masses measuring 3 cm or less in diameter at contrast-enhanced CT were included. The DL algorithm was developed by using retrospective data from one hospital between 2009 and 2021, with patients randomly allocated in a training and internal test set ratio of 8:2. Between 2013 and 2021, external testing was performed on data from five independent hospitals. A prospective test set was obtained between 2021 and 2022 from one hospital. Algorithm performance was evaluated by using the area under the receiver operating characteristic curve (AUC) and compared with the results of seven clinicians using the DeLong test. Results A total of 1703 patients (mean age, 56 years ± 12 [SD]; 619 female) with a single renal mass per patient were evaluated. The retrospective data set included 1063 lesions (874 in training set, 189 internal test set); the multicenter external test set included 537 lesions (12.3%, 66 benign) with 89 subcentimeter (≤1 cm) lesions (16.6%); and the prospective test set included 103 lesions (13.6%, 14 benign) with 20 (19.4%) subcentimeter lesions. The DL algorithm performance was comparable with that of urological radiologists: for the external test set, AUC was 0.80 (95% CI: 0.75, 0.85) versus 0.84 (95% CI: 0.78, 0.88) (P = .61); for the prospective test set, AUC was 0.87 (95% CI: 0.79, 0.93) versus 0.92 (95% CI: 0.86, 0.96) (P = .70). For subcentimeter lesions in the external test set, the algorithm and urological radiologists had similar AUC of 0.74 (95% CI: 0.63, 0.83) and 0.81 (95% CI: 0.68, 0.92) (P = .78), respectively. Conclusion The multiphase CT-based DL algorithm showed comparable performance with that of radiologists for identifying benign small renal masses, including lesions of 1 cm or less. Published under a CC BY 4.0 license. Supplemental material is available for this article.

Transition-Metal-Catalyzed C-C Bond Formation from C-C Activation.

ConspectusC-C single bonds are ubiquitous in organic compounds. The activation and subsequent functionalization of C-C single bonds provide a unique opportunity to synthesize conventionally inaccessible molecules through the rearrangement of carbon skeletons, often with a favorable atom and step economy. However, the C-C bonds are thermodynamically and kinetically inert. Consequently, the activation of C-C bonds is particularly attractive yet challenging in the field of organic chemistry. In the past decade, we sought to develop efficient strategies to carry out transition-metal-catalyzed diverse C-C cleavage/C-C forming reactions and to obtain some insights into the intrinsic reactivities of different C-C bonds. With our efforts, readily available alcohols, carboxylic acids, and ketones served as suitable substrates for the catalytic C-C coupling reactions, which are reviewed in this Account. In 2009, we observed a Ni-catalyzed cross coupling of aryl nitriles with arylboronic esters through C-CN cleavage. Encouraged by these results, we are interested in transition-metal-catalyzed C-C bond activation. Due to their broad availability, we then turned our attention to C-C cleavage of carboxylic acids. Rhodium-catalyzed decarbonylative coupling of carboxylic acids with (hetero)arenes was then achieved through oxidative addition of in situ formed, more reactive mixed anhydrides to Rh(I) without the need for oxidants that are commonly required for the decarboxylative coupling of carboxylic acids. Subsequently, the decarbonylation of more challenging unstrained aryl ketones was realized under Rh catalysis assisted by N-containing directing groups. Following this work, a group exchange of aryl ketones with carboxylic acids was achieved through 2-fold C-C bond cleavage. By employing the chelation strategy, Rh-catalyzed C-C bond activation of secondary benzyl alcohols was also accomplished through ß-carbon elimination of the rhodium alcoholate intermediates. The competing oxidation of secondary alcohols to ketones via ß-hydrogen elimination of the same intermediates was suppressed as thermodynamically favorable five-membered rhodacycles are formed after ß-carbon elimination. Different types of transformations of alcohols, including the Heck-type reaction with alkenes, cross coupling with arylsilanes, and Grignard-type addition with aldehydes or imines, have been achieved, showing the great potential of secondary alcohols in the formation of C-C bonds. These C-C bond-forming reactions are complementary to traditional cross couplings of aryl halides with organometallic reagents. However, these transformations produce small molecules as byproducts. To improve the atom economy, we then investigated C-C bond transformations of strained-ring cyclic compounds. Ni-catalyzed intermolecular cyclization of benzocyclobutenones with alkynes was recently achieved via the uncommon cleavage of the C1-C8 bond by employing a removable blocking strategy. Rh-catalyzed intramolecular annulation of benzocyclobutenols with alkynes was also achieved. In summary, our developments demonstrate the great potential of transition-metal-catalyzed C-C bond activation for the formation of new C-C bonds. To further expand the synthetic utility of C-C bond activation, more efforts are required to expand the substrate scope and to achieve earth-abundant metal-catalyzed transformations.

Oligomerization Mechanism of Methylglyoxal Regulated by the Methyl Groups in Reduced Nitrogen Species: Implications for Brown Carbon Formation.

Uncertain chemical mechanisms leading to brown carbon (BrC) formation affect the drivers of the radiative effects of aerosols in current climate predictions. Herein, the aqueous-phase reactions of methylglyoxal (MG) and typical reduced nitrogen species (RNSs) are systematically investigated by using combined quantum chemical calculations and laboratory experiments. Imines and diimines are identified from the mixtures of methylamine (MA) and ammonia (AM) with MG, but not from dimethylamine (DA) with the MG mixture under acidic conditions, because deprotonation of DA cationic intermediates is hindered by the amino groups occupied by two methyl groups. It leads to N-heterocycle (NHC) formation in the MG + MA (MGM) and MG + AM (MGA) reaction systems but to N-containing chain oligomer formation in the MG + DA (MGD) reaction system. Distinct product formation is attributed to electrostatic attraction and steric hindrance, which are regulated by the methyl groups of RNSs. The light absorption and adverse effects of NHCs are also strongly related to the methyl groups of RNSs. Our finding reveals that BrC formation is mainly contributed from MG reaction with RNSs with less methyl groups, which have more abundant and broad sources in the urban environments.

Interfacial engineering of transition metal dichalcogenide/carbon heterostructures for electrochemical energy applications.

To support the global goal of carbon neutrality, numerous efforts have been devoted to the advancement of electrochemical energy conversion (EEC) and electrochemical energy storage (EES) technologies. For these technologies, transition metal dichalcogenide/carbon (TMDC/C) heterostructures have emerged as promising candidates for both electrode materials and electrocatalysts over the past decade, due to their complementary advantages. It is worth noting that interfacial properties play a crucial role in establishing the overall electrochemical characteristics of TMDC/C heterostructures. However, despite the significant scientific contribution in this area, a systematic understanding of TMDC/C heterostructures' interfacial engineering is currently lacking. This literature review aims to focus on three types of interfacial engineering, namely interfacial orientation engineering, interfacial stacking engineering, and interfacial doping engineering, of TMDC/C heterostructures for their potential applications in EES and EEC devices. To accomplish this goal, a combination of experimental and theoretical approaches was used to allow the analysis and summary of the fundamental electrochemical properties and preparation strategies of TMDC/C heterostructures. Moreover, this review highlights the design and utilization of the interfacial engineering of TMDC/C heterostructures for specific EES and EEC devices. Finally, the challenges and opportunities of using interfacial engineering of TMDC/C heterostructures in practical EES and EEC devices are outlined. We expect that this review will effectively guide readers in their understanding, design, and application of interfacial engineering of TMDC/C heterostructures.

2D Mesoporous Zincophilic Sieve for High-Rate Sulfur-Based Aqueous Zinc Batteries.

Sulfur-based aqueous zinc batteries (SZBs) attract increasing interest due to their integrated high capacity, competitive energy density, and low cost. However, the hardly reported anodic polarization seriously deteriorates the lifespan and energy density of SZBs at a high current density. Here, we develop an integrated acid-assisted confined self-assembly method (ACSA) to elaborate a two-dimensional (2D) mesoporous zincophilic sieve (2DZS) as the kinetic interface. The as-prepared 2DZS interface presents a unique 2D nanosheet morphology with abundant zincophilic sites, hydrophobic properties, and small-sized mesopores. Therefore, the 2DZS interface plays a bifunctional role in reducing the nucleation and plateau overpotential: (a) accelerating the Zn2+ diffusion kinetics through the opened zincophilic channels and (b) inhibiting the kinetic competition of hydrogen evolution and dendrite growth via the significant solvation-sheath sieving effect. Therefore, the anodic polarization is reduced to 48 mV at 20 mA cm-2, and the full-battery polarization is reduced to 42% of an unmodified SZB. As a result, an ultrahigh energy density of 866 Wh kgsulfur-1 at 1 A g-1 and a long lifespan of 10,000 cycles at a high rate of 8 A g-1 are achieved.

Ethylene Electrooxidation to 2-Chloroethanol in Acidic Seawater with Natural Chloride Participation.

Ethylene oxidation to oxygenates via electrocatalysis is practically promising because of less energy input and CO2 output compared with traditional thermal catalysis. However, current ethylene electrooxidation reaction (EOR) is limited to alkaline and neutral electrolytes to produce acetaldehyde and ethylene glycol, significantly limiting cell energy efficiency. Here, we report for the first time an EOR to 2-chloroethanol product in a strongly acidic environment with natural seawater as an electrolyte. We demonstrate a 2-chloroethanol Faradaic efficiency (FE) of ∼70% with a low electrical energy consumption of ∼1.52 × 10-3 kWh g-1 over a commercial Pd catalyst. We establish a mechanism to evidence that 2-chloroethanol is produced at low potentials via direct interaction of adsorbed chloride anions (*Cl) with ethylene reactant because of the high coverage of *Cl during reaction. Importantly, this differs from the accepted multiple step mechanism of subsequent chlorine oxidation and ethylene chlorination reactions at high potentials. With highly active Cl- participation, the production rate for 2-chloroethanol in acidic seawater is a high 26.3 g m-2 h-1 at 1.6 V operation. Significantly, we show that this is 223 times greater than that for ethylene glycol generation in acidic freshwater. We demonstrate chloride-participated EOR in a proton exchange membrane electrolyzer that exhibits a 68% FE for 2-chloroethanol at 2.2 V operation in acidic seawater. This new understanding can be used for designing selective anode oxidation reactions in seawater under mild conditions.

Activity and Selectivity Roadmap for C-N Electro-Coupling on MXenes.

Electrochemical coupling between carbon and nitrogen species to generate high-value C-N products, including urea, presents significant economic and environmental potentials for addressing the energy crisis. However, this electrocatalysis process still suffers from limited mechanism understanding due to the complex reaction networks, which restricts the development of electrocatalysts beyond trial-and-error practices. In this work, we aim to improve the understanding of the C-N coupling mechanism. This goal was achieved by constructing the activity and selectivity landscape on 54 MXene surfaces by density functional theory (DFT) calculations. Our results show that the activity of the C-N coupling step is largely determined by the *CO adsorption strength (Ead-CO), while the selectivity relies more on the co-adsorption strength of *N and *CO (Ead-CO and Ead-N). Based on these findings, we propose that an ideal C-N coupling MXene catalyst should satisfy moderate *CO and stable *N adsorption. Through the machine learning-based approach, data-driven formulas for describing the relationship between Ead-CO and Ead-N with atomic physical chemistry features were further identified. Based on the identified formula, 162 MXene materials were screened without time-consuming DFT calculations. Several potential catalysts were predicted with good C-N coupling performance, such as Ta2W2C3. The candidate was then verified by DFT calculations. This study has incorporated machine learning methods for the first time to provide an efficient high-throughput screening method for selective C-N coupling electrocatalysts, which could be extended to a wider range of electrocatalytic reactions to facilitate green chemical production.

Direct Incorporation of Dinitrogen into an Aliphatic C-H Bond.

The activation of dinitrogen (N2) and direct incorporation of its N atom into C-H bonds to create aliphatic C-N compounds remains unresolved. Incompatible conditions between dinitrogen reduction and C-H functionalization make this process extremely challenging. Herein, we report the first example of dinitrogen insertion into an aliphatic Csp3-H bond on the ligand scaffold of a 1,3-propane-bridged [N2N]2--type dititanium complex. Mechanistic investigations on the behaviors of dinuclear and mononuclear Ti complexes indicated the intramolecular synergistic effect of two Ti centers at a C-N bond-forming step. Computational studies revealed the critical isomerization between the inactive side-on N2 complex and the active nitridyl complex, which is responsible for the Csp3-H amination. This strategy maps an efficient route toward the future synthesis of aliphatic amines directly from N2.

C2+ Selectivity for CO2 Electroreduction on Oxidized Cu-Based Catalysts.

Design for highly selective catalysts for CO2 electroreduction to multicarbon (C2+) fuels is pressing and important. There is, however, presently a poor understanding of selectivity toward C2+ species. Here we report for the first time a method of judiciously combined quantum chemical computations, artificial-intelligence (AI) clustering, and experiment for development of a model for the relationship between C2+ product selectivity and composition of oxidized Cu-based catalysts. We 1) evidence that the oxidized Cu surface more significantly facilitates C-C coupling, 2) confirm the critical potential condition(s) for this oxidation state under different metal doping components via ab initio thermodynamics computation, 3) establish an inverted-volcano relationship between experimental Faradaic efficiency and critical potential using multidimensional scaling (MDS) results based on physical properties of dopant elements, and 4) demonstrate design for electrocatalysts to selectively generate C2+ product(s) through a co-doping strategy of early and late transition metals. We conclude that a combination of theoretical computation, AI clustering, and experiment can be used to practically establish relationships between descriptors and selectivity for complex reactions. Findings will benefit researchers in designing electroreduction conversions of CO2 to multicarbon C2+ products.

Boosted Photoreforming of Plastic Waste via Defect-Rich NiPS3 Nanosheets.

Sustainable conversion of plastic waste to mitigate environmental threats and reclaim waste value is important. Ambient-condition photoreforming is practically attractive to convert waste to hydrogen (H2); however, it has poor performance because of mutual constraint between proton reduction and substrate oxidation. Here, we realize a cooperative photoredox using defect-rich chalcogenide nanosheet-coupled photocatalysts, e.g., d-NiPS3/CdS, to give an ultrahigh H2 evolution of ∼40 mmol gcat-1 h-1 and organic acid yield up to 78 µmol within 9 h, together with excellent stability beyond 100 h in photoreforming of commercial waste plastic poly(lactic acid) and poly(ethylene terephthalate). Significantly, these metrics represent one of the most efficient plastic photoreforming reported. In situ ultrafast spectroscopic studies confirm a charge transfer-mediated reaction mechanism in which d-NiPS3 rapidly extracts electrons from CdS to boost H2 evolution, favoring hole-dominated substrate oxidation to improve overall efficiency. This work opens practical avenues for converting plastic waste into fuels and chemicals.

Time-of-Flight Intracranial MRA at 3 T versus 5 T versus 7 T: Visualization of Distal Small Cerebral Arteries.

Background Three-dimensional (3D) time-of-flight (TOF) MR angiography (MRA) at 7 T has been reported to have high image quality for visualizing small perforating vessels. However, B1 inhomogeneity and more physiologic considerations limit its applications. Angiography at 5 T may provide another choice for intracranial vascular imaging. Purpose To evaluate the image quality and cerebrovascular visualization of 5-T 3D TOF MRA for visualizing intracranial small branch arteries. Materials and Methods Participants (healthy volunteers or participants with a history of ischemic stroke undergoing intracranial CT angiography or MRA for identifying steno-occlusive disease) were prospectively included from September 2021 to November 2021. Each participant underwent 3-T, 5-T, and 7-T 3D TOF MRA with use of customized MR protocols within 48 hours. Radiologist scoring from 0 (invisible) to 3 (excellent) and quantitative assessment were obtained to evaluate the image quality. The Friedman test was used for comparison of characteristics derived from 3 T, 5 T, and 7 T. Results A total of 12 participants (mean age ± SD, 38 years ± 9; nine men) were included. Visualizations of the distal arteries and small vessels at 5-T TOF MRA were significantly higher than those at 3 T (median score: 3.0 vs 2.0, all P < .001 for distal segments and lenticulostriate artery; median score: 2.0 vs 0, P < .001 for pontine artery). The total length of small vessel branches detected at 5 T was larger than that at 3 T (5.1 m ± 0.7 vs 1.9 m ± 0.4; P < .001). However, there was no evidence of a significant difference compared with 7 T in either the depiction of distal segments and small vessel branches (average median score, 2.5; all P > .05) or the quantitative measurements (total length, 5.6 m ± 0.5; P = .41). Conclusion Three-dimensional time-of-flight MR angiography at 5 T presented the capability to provide superior visualization of distal large arteries and small vessel branches (in terms of subjective and quantitative assessment) to 3 T and had image quality similar to 7 T. © RSNA, 2022 Online supplemental material is available for this article. An earlier incorrect version appeared online. This article was corrected on September 14, 2022.

Mild Methane Electrochemical Oxidation Boosted via Plasma Pre-Activation.

Obtaining partial methane oxidation reaction (MOR) with various oxygenates via a mild electrochemical method is practically difficult because of activation of stable C─H bond and consequent reaction pathway regulation. Here, a real-time tandem MOR with cascaded plasma and electrocatalysis to activate and convert the methane (CH4 ) synergistically is reported for the first time. Boosted CH4 conversion is demonstrated toward value-added products including, alcohols, carboxylates, and ketone via use of commercial Pd-based electrocatalysts. Compared with hash industrial processes, a mild condition, that is, anode potential < 1.0 V versus RHE (reversible hydrogen electrode) is used that mitigates overoxidation of oxygenates and obviates competing reaction(s). One evidence that Pd(II) sites and surface adsorbed hydroxyls are important in facilitating activated-CH4 species conversion, and establish a reaction mechanism for conversion(s) that involves coupling reactions between adsorbed hydroxyls, carbon monoxide and C1 /C2 alkyls. One conclude that pre-activation is important in boosting electrochemical partial MOR under mild conditions and will be of benefit in the development of sustainable CH4 conversion technology.

Distance-Triggered Distinct Aryl Migrations on Azidodiboranes.

Derived from structurally similar precursors, two different azidodiboranes went through distinct aryl migration reactions triggered by different boron-boron separation distances. Biphenylene based diborane with a shorter boron-boron distance underwent heterolateral aryl migration to form a seven-membered azadiborepin, while xanthrene based diborane with a longer boron-boron distance afforded a stable bis-azidoborane scaffold. The pyrolysis of such a bis-azidoborane led to eight-membered oxazadiborocine through homolateral aryl migration and subsequent [3+2] cycloaddition. Density functional theory (DFT) calculations unveiled that the boron-boron separation distances were the intrinsic factors for the distinct migrations.

Neutral Boryl Radicals in Mixed-Valent B(III) Br-B(II) Adducts.

The general strategies to stabilize a boryl radical involve single electron delocalization by π-system and the steric hinderance from bulky groups. Herein, a new class of boryl radicals is reported, with intramolecular mixed-valent B(III) Br-B(II) adducts ligated by a cyclic (alkyl)(amino)carbene (CAAC). The radicals feature a large spin density on the boron center, which is ascertained by EPR spectroscopy and DFT calculations. Structural and computational analyses revealed that the stability of radical species was assisted by the CAAC ligand and a weak but significant B(III)Br-B(II) interaction, suggesting a cooperative avenue for stabilization of boryl radicals. Two-electron reduction of these new boryl radicals provides C-H insertion products via a borylene intermediate.